The present invention relates to a safety switch mounted on a peripheral wall surface of a protective door of, for example, industrial machinery etc., and stopping a supply of power to the industrial machinery etc. when the protective door is opened.
Conventionally, the protective door etc. of industrial machinery has been provided with a safety switch preventing the machinery from being driven in situations where the protective door is not fully closed in order to avert accidents wherein a worker is injured as a result of entrapment in the machinery. As an example of this type of safety switch, the safety switch disclosed in Patent Document 1 is provided with a lock mechanism that mechanically locks an operating key after the operating key has been inserted into the safety switch, thus preventing extraction of the operating key.
A safety switch provided with this lock mechanism is electrically connected to industrial machinery such as a robot and includes a switch main unit (key switch) and an actuator (key); furthermore, the switch main unit is fixed to a peripheral wall surface of a protective door and the actuator is fixed to the protective door. A fixing position of the actuator at that time is set opposing a key insertion opening of the switch main unit and enabling entry into a head case at a top-left portion of the switch main unit when the protective door is in a closed condition.
Then, as a result of entry of the actuator, a contact disposed below the head case of the switch main unit switches to a closed condition and power is supplied to electrical machinery, allowing the machinery to be driven. Meanwhile, when the actuator withdraws as a result of opening of the protective door and is extracted from the head case, the integrated contact switches to an open condition, and the supply of power to the machinery is cutoff.
It should be noted that the head case is provided with a cam unit (drive cam) engaged with the actuator and rotating pursuant to entry and withdrawal of the actuator, and a follower disposed below the cam unit and moving vertically along an outer surface of the cam (cam curve section) as the cam unit rotates. Also, a working member and an operating member coupled to the follower and moving vertically and a contact opening and closing in a coupled manner with the operating member are provided inside the switch main unit disposed below the head case. Furthermore, the follower, the working member, and the operating member are urged upwards by a spring disposed in the vicinity of the operating member; the follower maintains sliding contact with the outer surface of the cam unit; the follower, the working member, and the operating member move vertically integrally pursuant to the rotation of the cam unit; and the contacts are switched between the open and closed conditions thereof in a coupled manner with this vertical motion.
In addition, this safety switch is also provided with a lock mechanism including a lock component (lock member), moving horizontally, an L-shaped lock lever, and a plunger. The lock lever is axially supported at a central portion thereof so as to be capable of freely rotating; a left end and a right end of the lock lever are connected so as to be capable of freely rotating to a right end portion of the lock component and a lower end side of the plunger, respectively; and a motion of the plunger is transferred to the lock component via the rotation of the lock lever. Furthermore, the lock component is urged leftward by a spring. Accordingly, pursuant to rotation of the cam unit in a clockwise direction, the follower slides from a large diameter portion of the outer surface of the cam unit to a small diameter portion thereof, the operating member moves upward as a result of the urging of the spring, and in addition, the lock component moves leftward. Consequently, the lock component moves underneath the operating member, blocking downward motion thereof; the cam unit becomes engaged by the follower; the cam unit is held in a locked condition, prevented from rotating; and extraction of the actuator is blocked.
Furthermore, a magnetic solenoid for driving the plunger of the lock mechanism is disposed at an upper-right portion inside the switch main unit, and the plunger is moved up and down as a result of energizing of the magnetic solenoid being started and stopped, respectively, by external control. Then, the magnetic solenoid is non-energized with the cam unit in the locked condition, and if the condition of the magnetic solenoid is changed from non-energized to energized, the plunger moves upward as a result of the magnetic attraction force thereof, the lock lever rotates in a counter-clockwise direction as a result of the upward motion of the plunger, the lock member moves rightward as a result thereof, allowing the operating member to move down and the cam unit to rotate in a counter-clockwise direction. Consequently, the cam unit is released from the locked condition to an unlocked condition and the actuator can be extracted.
Patent Document 1: JP H9-245584A ([0035] to [0044], FIG. 1)